Process for making plates for color printing



PROCESS FOR MAKING PLATES FOR COLOR PRINTING Filed Jan. 9, 19-37 3Sheets-Sheet l INVENTOR. E/ERETTIZPEA ro/v,

ATTORNEYS y y E. R. EATON 2,122,859

PROCESS FOR MAKING PLATES FOR COLOR PRINTING Filed Jan. 9, 1957' 3Sheets-Sheet 2 fisksrrfaE/qrolv.

ATTORNEYS INVENTOR? g "Q July 5, 1938. E. R. EATON 2,122,859

PROCESS FOR MAKING PLATES FOR COLOR PRINTING Filed Jan. 9, 1957 3Sheets-Sheet 3 INVENTOR. EVERETTE. 5470M ATTORNEYS Patented July 5, 1938UNITED STATES PROCESS FOR MAKING PLATES FOR COLOR PRINTING Everett R.Eaton,

McCall Corporation,

poration of Delaware Darien, Conn., assignor to New York, N. Y., a cor-Application January 9, 1937, Serial No. 119,736

4 Claims.

My invention relates to the preparation by photoengraving of plates forprinting in color and more particularly to processes for blocking outcertain areas in making plates for half-tone printing. 7

In multicolor printing, successive impressions in different colors aresuperimposedj the colors generally being the three primary colors, andblack. Shades such as green or purple are formed by the superposition ofappropriate shades or tones of the respective primary colors of whichthey are constituted. Each impression is made by a separate plate havingprinting areas to print its respective color where the color is toappear in the final picture and with a depth of intensity to correspondwith the color efiect desired. Areas of one plate may coincide with oroverlap areas of another plate to produce an intermediate shade. Forexample, in producing an area of a green color or shade it will beprinted with both blue and yellow. These various areas must be exactlypositioned since if one, for example, the blue area, is slightly oiTsetthe resulting composite shade, of green, will have an unwanted margin ofblue.

In making the printing plates by photoengraving, a negative of anoriginal color sketch or picture is made for each plate by using afiltered light so that light is reflected from those areas of the sketchor picture in which the respective color appears either in a pure coloror in a composite color. For example the negative for printing the bluecolor would be formed by light not only from areas of pure blue but fromareas of green, violet, lavender and similar tints. Similarly thenegative for the yellow plate would include areas of green and orange,and the negative for the red plate would include areas of orange andpurple shades. The intensity of the color must be appropriately varied,not only for the pure shades but also for the composite color shades.For example a green or a blue green would have light or lighter shadesof yellow, and a purple or reddish purple would have correspondinglylighter shades than that for the pure color areas. In half-toneprinting, in which a screen is inserted between the sketch and thenegative so that the light reflected 'irom the sketch passes onlythrough the meshes of the screen and is then separated into separatepencils of light, the negative is formed of dots of varying size tocorrespend with the respective light intensities and the resultingprinting plate surface has projections of corresponding areas.

In practice, however, the reproduction of the colors obtained by merelyphotoengraving in this manner is not exactly due to the inability of thefiltered light to reflect the selected color faithfully and to excludeall others, or to other causes or to a combination of causes. Platesmade by 5 merely photographing with the selected filtered light wouldproduce pictures that would be off color in whole or in part for examplebeing too 7 dark or having areas in which a color such as red or blue istoo prominent or too weak. The plates 10 must, therefore, be etchedselectively by hand to eliminate or block out certain areas and bringout or emphasize others. Heretofore this has been a difficult taskrequiring a high degree of skill and with a danger that areas ofseparate plates for composite shades or colors, such as green or orange,may not exactly coincide and thus may produce offsh'ade margins.

For example, if certain parts are to be blocked out on the etched plate,it is necessary to protect those parts that are to be retained and thento etch away the parts to be eliminated. It is, however, diflicult forthe etcher to find and accurately paint in on a chalked up etched plate,particularly when the detail is smaller than the original sketch due toreduction in size. Also in certain tones as for example those borderingon pure white, it is frequency very hard to find the outlines of theareas and to hold such fine distinctions in tone particularly in light,or near white, shades.

In my present invention these difliculties are eliminated to a verylarge extent and a process is provided in which the elimination of aparticular color is greatly facilitated and the correspondence in areaof two superposed colors made substantially certain.

In my process, in making the negatives from a colored sketch, atransparent thin sheet of Celluloid is superposed on the original sketchor pic- 40 ture and provided with identification marks to ensureaccurate realignment and then those areas in which the selected color tobe printed appear are outlined as for example with India ink. Theoutlined areas are then covered with a black color, preferably on thereverse side so as to produce a perfect black, and then replaced on theoriginal sketch. An exposure of the sketch with the superposed blockedout Celluloid sheet is then taken on the negative, the half-tone screenbeing removed or placed out of focus. Preferably a sheet of white paperisinserted between the Celluloid and the skitch to produce a perfectlyblack and white object. This gives a dead exposure to all of the areasexcept the blockedout areas.

- a similar manner. The processis then repeated picture I 2. Theseregister marks upon all of the areas that are taking a negative exposurefirst in dead black and white with both Celluloid sheets and thenthrough the half-tone screen with the Celluloid and paper removed. Foreach color there will, therefore, be a transparent or celluloid blockoutsheet or a combination. of such sheets. As a result an area of compositecolor, for example, green, will .be blocked out on the Celluloid sheetfor blue and this sheet will also be used for yellow so that a secondblocking out of this area is not required but only those additionalareas in which yellow is to appear without blue. If yellow is not toappear at any area where the blue has been blocked out, it can becovered on its appropriate Celluloid sheet by dead white paint, such asChinese white. This will have the same effect as though it had not beenblocked out. .By using combinations of Celluloid block-out sheets thenecessity of blocking out an area twice is avoided and correspondinglydanger of variation in the blocking out of an area for two differentcolors is eliminated and all areas for composite colors are identical.

The various features of the invention are illustrated by way of examplein the accompanying drawings in which Fig. 1 is a view of an originalsketch and a transparent sheet superimposed thereon with certain colorareas outoutlined for blocking out. Fig. 2 is a view of the reverse sideof the Celluloid plate showing the manner of blocking out. Fig. 3 is aview of the blocked out sheet the white sheet being inserted between thetwo. Fig. 4 is a view showing the manner of photographing the originalsketch and Celluloid sheet assembly. Fig. 5 is a similar view showingthe photographing through a half-tone screen of the sketch with theCelluloid sheet removed Fig. 6

is a sketch with a second transparent sheet superimposed on the firstsheet for blocking out a second color, and Figs. 7 and 8 show furthercombinations of Celluloid sheets for additional colors.

Referring to .the accompanying drawings, register marks l0 and II areplaced on a sketch or Ill and H are preferably in the form of a crossmade with a fine ruling pen. 'Ihen a transparent sheet l3 such as asheet of Celluloid of a thickness of .005 of an inch is superposed onthe sketch l2 and suitably secured as with decorators Scotch tape.Register marks are placed on this sheet to correspond with the registermarks l0 and H of the original, care being taken to have them in perfectalignment with the original. Thereto retain a tone for the particularcolor selected are outlined as at l4, l5, l6, l1 and I8. For example, ifa blue plate is to be madethese areas would be those containing blue orsome color containing blue, as for example green or violet. These areasare then filled in by a black coating. To obtain the blackest efiect inthese areas the Celluloid sheet is removed and turned over and cellulosereplaced on the original sketch,

opaque or similar covering material is filled in on the reverse side ofthe cellulose sheet covering the areas outlined.

For example, as shown in Fig. 2, the area Hi is being filled in orblocked out and the areas l4, l5, I1 and I8 will be similiarly opaqued.Then the Celluloid sheet or mask thus formed is placed in its originalposition on the sketch l2, the register marks I0 and l l of the maskbeing carefully positioned to coincide with those of the originalsketch. The mask is firmly secured by Scotch tape. The areas of thesketch which are to contain the tones of the color whose plate is to bemade are therefore now covered with black. To produce a black and whiteobject, a sheet of white paper I9 is inserted between the Celluloid maskand the original sketch. As shown in Fig. 3, this covers up with whitethose areas of the sketch that are not blocked out.

Fig. 3 shows the process duringthe step of inserting the paper and itseffect in changing the assembly to a pure black and White object. Thesheet of paper will be either sufficiently short not to cover theregister marks ill and II, or will have openings through which thesemarks can be seen. In the latter case the paper may be placed on thesketch and the mask then mounted on it. The assembly of mask andoriginal is now ready for first exposure to the negative.

Although no special equipment is necessary, a glass front tiltingcopyboard is desirable for producing the best results. The operator orcameraman first places the original copy on the board fastening it intoposition so that there will be no danger of its moving later on. Thismay be fastened with adhesive tape or Scotch tape. Over the original 2.sheet of white paper may be placed, openings being provided throughwhich the register marks can be seen. The Celluloid mask is then placedin position with its register marks coinciding exactly with those of theoriginal. Over this assembly there is then placed a sheet of plate glassto hold the Celluloid mask in close contact with the original copy.

With the plates thus prepared, the operator makes an exposure on asensitive plate with the half-tone screen either entirely removed ormoved to such position that it does not form the light rays from theoriginal into pencils but diffuses it. This is preferable to entirelyremoving the screen as it does not require any change in the focus ofthe camera. A sufiicient distance for the screen in this operation isapproximately halt the distance between the normal distance of thescreen from'the sensitive plate for half-tone work and the. greatestdistance which the camera adjustment permits.

The positioning of the original I2, the screen I 9 and the camera 20 as.shown in Fig. 4 illustrates the arrangement for this exposure. Theexposure is continued sufliciently long so that those parts in theoriginal and mask assembly that appear white will cause a dense opaqueblack area in the negative. After this first exposure has been completedthe lens is capped, the screen moved back to its proper position asshown in Fig. 5, the Celluloid mask and white sheet of paper removedfrom the original and a half-tone exposure is made on the negative inthe usual manner; thereupon the negative is developed,

Celluloid mask' and dense and opaque without semblance of dot' formationin those areas which were not blocked in in the mask. A print on copperis then made from this negative in the usual manner after which theetcher spots up the plate,

paints in dead metal leaving the usual s" channel around the liveportions, coats the back with an acid-resisting ink and flat etches theplate. Then the plate is deep etched and cleaned off and is ready forwhatever staging and re-etching are required to balance the colors onthe various plates. After this is completed the plate is ready to betrimmed, routed and proved in the usual manner.

In making the next color plate, for example, yellow, as indicated inFig. 6, the mask I3 is placed on the original sketch l2 and fixed inplace with the register marks exactly registering, then a secondCelluloid sheet 2| is placed on the mask l3. There will be certainareas, for example, green, which must be blocked out for yellow as wellas for blue, but having beenblocked out in the mask l3 do not need to beadditionally blocked out on the mask to be formed on the sheet 2|.Certain additional areas, however,'may have yellow in a colorcombination and not blue, as for example in pure yellow or orange.Assuming, therefore, that the areas l6 and II are green and that theadjacent borders 22 and 23 are orange these would now be blocked out ina manner similar to the areas l6 and I1. The stocking areas 24 and theflesh colored areas, such as the hands and face 26, might also beblocked out for the yellows. If there are any parts that have beenblocked out for blue and which are not to contain any yellow, theseareas may be covered with'Chinese white on the mask 2| which will havethe effect of eliminating the blocking on the mask I3. When this hasbeen completed and opaqued the two masks are placed on the original, thewhite sheet 19 again inserted and the two exposures made; thereupon theprinting plate may be made as described above,

To make a plate for the red, the masks l3 and 2lmay be replaced, carebeing taken to register both of them on the register lines and a thirdtransparent Celluloid sheet 21 superposed on them. All areas containingblue and yellow are already blocked out by the masks l3 and 2|, and itis only necessary to block out those additional areas which are tocontain the red color. As the areas 22, 23 and 24 have been blocked outfor the yellows, as have also the areas 25 and 25 which may contain somered, it is only necessary to block out the additional areas that containred but not yellow or blue. Such, for example, might be cuff areas 28. Anegative is thereupon made by double exposure and a plate made in themanner described above.

In making the fourth or black plate, still another sheet 29 is placed on7 and those additional parts of the sketch which are to be printed inblack are blocked out. If any areas are to appear in pure white, theymay remain unblocked as, for example, the neck band area 30 and thehandkerchief 3|. A negative is again made by double exposure of theassembly and the original sketch and a plate made as described above.Areas which appear in black are blocked out as shown at 3| and 32.

In the event that the sketch contains no combination of blue and red sothat there are no areas blocked out for these two colors, but doescontain combinations of blue and yellow and red and yellow, the mask l3might be omitted colors.

the assembly of Fig.

from the red mask, that is, it would be omitted from the assembly shownin Fig. '7.

In some cases it may bemore convenient to combine certain masks toproduce each of the For example, each color mask may be made up of oneor more masks. This enables a greater flexibility to be obtained withoutthe necessity of blocking out certain areas with Chinese white or whitepigment. For example, a series of three masks might be used in which thered would be made of masks I and II, the black of'masks I and II, theyellow of masks I, II and III, and the blue of masks II and III.

In this case it will be apparent that the mask I covers combinations ofyellow and red and incidentally black; mask II covers any combinationsof red, yellow and blue as well as black; mask III covers combinationsof yellow and blue. In any event those areas that contain more than onecolor tone require blocking in only once. This not only has theadvantage of eliminating the labor of blocking, which may beconsiderable for a complicated design such as a flowered or other finedesign, but it ensures perfect alignment of these two areas. As theareas are made in outline directly on the. original, it is relativelyeasy to trace these outlines even through they are between relativelylight shades and pure white. Vignetted outlines may, therefore, betraced with perfect accuracy.

This avoids the necessity .for the etcher to pick out on a plate, whichmay be reduced in size, an exact spot corresponding for example toyellow on the original sketch. Because the colors have been separated,that is the reds from the greens, the yellows from the purples, etc., itis advantageous to get a proof of the work directly after the plateshave been fiat etched and deep etched. With this proof as a guide theetcher can the more easily and more quickly balance the colors to matchthe original.

What I claim is:

1. A process of photographically forming a negative for a halftoneprinting plate for multicolor printing, from a colored original whichcomprises forming a number of masks each comprising a transparent sheethaving at least one black opaque area, the black opaque area of eachmask being different in outline and position from the black opaque areaof the other said masks to block out all areas of the original of aselected hue, exposing a light sensitive element in a camera first tosaid original through a combination of more than one of said maskssuperimposed in register to block out the combined opaqued areas of thecombination of masks covering all areas of the original containing thecolor value of the plate to be made and then exposing said lightsensitive element to said original without said masks normal position toof a selected color through a halftone screen in obtain a halftonenegative value.

2. A process of photographically forming a printing plate for multicolorprinting from a colored original which comprises forming a number ofmasks each comprising a transparent sheet having at least one blackopaque area, the black opaque area of each mask being different inoutline and position from the black opaque area of the other said maskstoblock out all areas of the original of a selected hue, exposing alight sensitive element in a camera first to said original through acombination of more than one of said masks superimposed in register toblock out the combined opaqued areas of the combination of maskscovering all areas of the original containing the color value of theplate to be made and then exposing said light sensitive element to saidoriginal through a halftone screen in normal position without said masksto obtain a halftone negative of a selected color value, developing andfixing the resulting negative and photoengraving a print therefrom.

3. The process of claim 2, in which a proof is taken of said printingplate and said printing plate is then re-etched to modify the colortones. 4. The process of claim 1, in which a white opaque sheet isinserted in the assembly of masks and original between the original andits superposed masks during the first exposure thereof.

EVERE'I'I R. EATON.

